1. Field of the Invention
The present invention relates to a head-mounted display. More particularly, the present invention relates to a head-mounted display that can view virtual images, when worn by a user.
2. Description of the Related Art
In general, a head-mounted display (HMD) is a device that is worn by a user and displays an image in front of the user's eyes in a virtual reality system or an augmented reality system. The HMD generally is embodied in the form of protective goggles or a helmet.
Referring to FIG. 1, a conventional HMD 10 includes a main body 20, and a left eye unit 30a and a right eye unit 30b that are connected thereto. The main body 20 is formed such that the left eye unit 30a and right eye unit 30b are parallel to the main body 20. Reference numerals 400a and 400b indicate the left eye and right eye, respectively, of a user.
When using the HMD, the user is under the impression that a wide screen is being provided in front of their eyes and thus the HMD can be used as a portable individual display. Further, when using the HMD, the user can control a micro-computer through a three-dimensional virtual menu screen displayed through the HMD, instead of controlling the micro-computer through a two-dimensional display screen. For a virtual image, the HMD typically includes an image module, including a liquid crystal display (LCD) for generating an image and an optical system such as a lens for forming the generated image as a virtual image at a predetermined virtual distance from the user.
Due to variations in determining distances between several users operating the HMD, the conventional HMD has a problem in that the user may receive an impression that a screen of a virtual image is small and is positioned at a relatively close location. Specifically, the user identifies a distance from the user to the virtual image using a monocular focus method. In the monocular focus method, when an eyeball muscle adjusts so that a virtual image may be viewed most clearly, the distance is determined by the viewer's normal visual sense. However, the ability to determine distance of various users varies considerably between the users. A field of view (FOV), which is the angle formed by light after light emitted from opposite sides of the LCD passes through a lens of the optical system, is determined by a size of the LCD and magnification power of the lens. The FOV is hence determined according to a configuration of an optical system, and does not vary between users.
However, as described above, for the FOV predetermined according to a system configuration, different users experience a different screen size due to the variation in distance determination between the users, and some users may experience that a virtual image exists at a distance closer than a designed location, and thus these users will receive the impression that a screen of the virtual image is small.